The present disclosure is directed to a method for detecting chemicals, and, in particular, to a method of using Surface Enhanced Raman Spectroscopy (SERS) to detect, identify and/or determine concentrations of trace chemicals in oil and gas applications.
Petroleum is recovered from subterranean reservoirs through the use of drilled wells and production equipment. Oil and natural gas are found in, and produced from, porous and permeable subterranean formations, or reservoirs. Generally, the life cycle of an oil and/or gas well includes drilling to form a wellbore, casing, cementing, stimulation, and enhanced or improved oil recovery.
Many fluids are employed during the life cycle of an oil and/or gas well. For example, in order to improve extraction of oil and/or gas, well treatment additives are incorporated into various fluids utilized during the life cycle of an oil and/or gas well. The concentration of well treatment additives such as phosphonate scale inhibitors is currently measured by phosphorous content via Inductively Coupled Plasma (ICP) which measures the intensities of element-specific atomic emissions produced when the solution components enter the high-temperature plasma. Additional methods for detection of typical additives like scale and corrosion inhibitors include colorometric UV/visible spectroscopy, the hyamine turbidity chemical method, fluorescence, HPLC, HPLC/mass spectrometry (HPLC/MS), GC/MS (mainly corrosion inhibitors) and Time-Resolved Fluorescence (TRF). However, each of these methods has limitations in terms of the detection limit and specific analytes to be detected, and generally involve tedious data analysis, particularly HPLC/MS and GC/MS. What is needed are new methods which allow the determination of well treatment additives, particularly at low concentrations, which are applicable to a wide range of well additives, are not complex in terms of the method and data interpretation and can also be used on site for “near” on line measurements.